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Ch.2 - Atoms & Elements
Chapter 2, Problem 61

Fill in the blanks to complete the table. Symbol Ion Formed Number of Electrons in Ion Number of Protons in Ion Ca Ca2+ ______ ______ ______ Be2+ 2 ______ Se ______ ______ 34 In ______ ______ 49

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Identify the atomic number of each element to determine the number of protons in the neutral atom. For example, calcium (Ca) has an atomic number of 20, so it has 20 protons.
For each ion, determine the number of electrons by considering the charge. A Ca<sup>2+</sup> ion has lost 2 electrons, so it has 18 electrons (20 - 2).
For Be<sup>2+</sup>, the atomic number of Be is 4, so it has 4 protons. The ion has 2 electrons, indicating it has lost 2 electrons.
For Se, the atomic number is 34, so it has 34 protons. To find the ion formed, consider common oxidation states; Se typically forms Se<sup>2-</sup> by gaining 2 electrons, resulting in 36 electrons.
For In, the atomic number is 49, so it has 49 protons. Determine the ion formed by considering common oxidation states; In typically forms In<sup>3+</sup> by losing 3 electrons, resulting in 46 electrons.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Ionic Charge

Ionic charge refers to the electrical charge that an atom acquires when it loses or gains electrons to form an ion. For example, calcium (Ca) loses two electrons to form Ca²⁺, resulting in a positive charge. Understanding ionic charge is crucial for determining the number of electrons in an ion and how it relates to the number of protons.
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Protons and Electrons

Protons are positively charged particles found in the nucleus of an atom, and their number defines the atomic number of an element. Electrons are negatively charged particles that orbit the nucleus. In a neutral atom, the number of protons equals the number of electrons, but in ions, this balance is disrupted, leading to a net charge that must be accounted for when filling in the table.
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Neutron-Proton Ratio

Atomic Structure

Atomic structure refers to the arrangement of protons, neutrons, and electrons within an atom. The atomic number, which is the number of protons, determines the element's identity. For example, selenium (Se) has 34 protons, and understanding this structure helps in identifying the number of electrons in its ion form, which is essential for completing the table accurately.
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